Centrifugal switch



Allg. 4, R LEE CENTRIFUGAL SWITCH l/NVENTQR ROYAL. LEE

BY 4 Al l/VSULAT/ `Filed May 16, 1940- 26 J4 47 .31 .55 FIG PatentedAug. 4, 1942 2,291,639 caN'rmr'UGAL swrrcn Royal Lee, Milwaukee, Wis.,assignor to il.

Engineering Research Corporation, Milwaukee,

of Wisconsin Wis., a corporation Application May 16, 1940, .Serial No.335,461

(Cl. 20o-80) 8 Claims..

The present invention relates to speed-respon= sive devices andmoreparticularly to centrifugal switches.

It is an object of the invention to provide an improved centrifugalswitch which will operate smoothly -and accurately throughout a widerange of speed-settings.

A`Another object is to provide a centrifugal switch which can beeconomically manufactured' and which has an adequate currentwarryingcapacity.

The invention further consists in the several features hereinafterdescribed and claimed. In the accompanying drawing, illustrating cer-."/tain embodiments of the invention,

Fig. 1 is a sectional elevation showing one form of centrifugal switchconstructed in accordance with the invention, the switch being mountedon an electric motor and being adjusted for operation at high speed;

y Fig. 2 is a front elevation ci the switch;

Fig. 3 is a top view;

Fig. 4 is a bottom view;

Fig. 5 is a sectional elevation taken generally Fig. 6 is a sideelevation of the switch, parts being broken away and parts being shownin section, and the switch being adjusted for operation at low speed;

Fig. 'l is a side View, partly in section, oi a modied form ofcentrifugal switch, the switch being adjusted for operation at highspeed;

Fig. 8 is a front elevation of the switch ci Fig. "i, and

Fig. 9 is a top view, similar to Fig. 3, showing another form ofcentrifugal switch in which the contacts are adapted to engage uponincrease of lmounted on the rotatable member il and are preferably inthe form of flat concentric collector rings or disks mounted on one sideci the insulating disk i9. As seen in Fig. l, brushes 2.5i and 24 bearon the respective collector rings il and 22 and are here shown to becarried by the motor frame.

Rigidly secured to 'the insulating disk lil, by a plurality ofrivet-forming studs or posts le and cooperating screws is a generallycircular, ill-shaped frame or plate 2l which is formed oi a suitablemetal such as duralumin. The studs or pests 2li also serve to secure theouter collector ring, 2l, to the insulating disls and to electricallyconnect the metal frame 2l to this collector ring. The t3-shaped frame2l extends at right-angles to the disk anis and in spaced relation tothe disls, and has a gap between its ends. A plurality of contacts @ilare detachably secured to the spaced end portions oi the plate El in oncenter relation to the dist. axis and have their contact faces lying ina plane normal to the disk axis. The Contact heads are preferably formedof. tungsten or other resistant metal. ln the present instance, each endportion o the plate is shown to carry two contacts. A balancing segnientSii is secured to the plate 2T! at the peripheral region thereofdlametrically opposite the contacts 2Q.

lDisposed. between the insulating disk i9 and metal frame ill is aiorlsed, plate-like, oscillatory lever which is hingedly supported onthe insu-s lating disk by a pau of rivet-fore posts or studs 32 andcooperating screws engaging the ends of a irl-shaped hinge-orming leafspring to, the latter being riveted or otherwise secured to sideextensions oi the lever. The :trame 2l is provided with openings 35 foraccess to the screws 33. The plane oi the lever 3i is approximately atright angles to the anis of the disk, and the longitudinal center lineoi the lever eX- tends diametrically with respect to the disls axis. Theposts or studs 32 also serve to secure the inner collector ring, 222, tothe insulating disk and to electricalliT connect the lever to thiscollector ring. The inner collector ring is further secured to thedisl:` by rivets 36. The lever 3i is formed of a suitable light-weightmetal such as duralumin. A plurality oi contacts el are detachablysecured to the free ends of forli arms of the lever 3l and cooperatewith the contacts 29 on the metal frame 2l, the lever contacts beingnormally urged or biased against the frame contacts by the hinge springtl. The eiective' hinge axis of the lever extends in a transversedirection with respect to the disl; axis and at one side of the diskaxis, while the contacts 3l are arranged at the opposite side of thedisk axis. The lever contacts are movable in a direction approximatelyparallel to the disk axis.

The oscillatory lever ll carries thereon a weighted centrifugallyactuated member 98 which is shiftable with respect to the lever toinoscillatory lever Il. as by means of a cross shaft 39 extendingparallel to the hinging axis of the oscillatory lever and having reducedends jour-v nailed in bearing members 40 secured to the fork arms of theoscillatory lever. The auxiliary lever 39 extends radially of the diskaxis and is movable in the space between the 'fork arms of the lever 9|and in the gap 29 between the ends of the c-shaped frame 21. 'I'he axisof the cross shaft 39 extends in the region between the disk axis andthe contacts. The outer end of the auxiliary lever 98 carries anoff-center weight member 4| which extends angularly in a direction awayfrom the insulatingv disk and which is secured to the lever by rivets42, one of these rivets also serving to lock the cross shaft 99 to theweight member. The inner end of the auxiliary lever 3l is disposed atthe axis of the disk and carries a rounded metal button 43 against whichis adapted to bear the rounded insulating tip 44 of an adjusting screw45, the latter extending axially of the disk and movable in the centralopen space of the c-shaped frame 21. In order to permit adjustment ofthe screw while the switch is operating, the screw is carried in astationary uscrew-threaded support 46. Inward movement of the inner endof the auxiliary lever Il is yieldingly resisted by a leaf spring 41which extends in a radial direction and. has its outer end riveted orotherwise secured to the hinged end portion of the oscillatory lever Il,the inner end of the spring 41 having an embossed rounded end whichbears on the inner side of the button 4I. The spring 41 holds the button43 against the tip 44of the adjusting screw 4l, and the inwarddisplacement of the spring by the screw serves to counteract the biasingforce of the hinge spring I4.

'Ihe centrifugal switch may be used in any suitable circuit and by wayof example it is here shown to be included in series with motor windingscomprising a pair of series field windings 4l and an interposed amature49, the field windings being connected to line conductors Il. 'I'hebrush 23 is connected by a conductor Il to one of the motor brushes andthe brush 24 is connected by a conductor I2 to one end of one of thefield windings 4I. thus placing the centrifugal switch in series withthe motor windings. In some instances the switch is shunted by aresistor Il and by a protective device such as a condenser I4. Byplacing the switch in circuit between the field windings, the latterwill form choke coils or reactors in both line conductors to prevent ormlnimize the tron to these conductors of electrical disturbances thatmay be caused by the operation of the switch. The motor windings may bethose of the motor Il or of a separate motor.

\ When the centrifugal switch of Figs. 1 to 8 is at rest the contacts l1are urged by their springmounted supporting lever 3l into engagementwith the contacts 29 carried on the frame 21. The contact engagementwill be maintained throughout the normal range of adjustment of thespeed-setting screw 49. For adjusting the switch to open at a high speedthe screw is turned outwardly to the position shown in Fig. 1, thuscausing the weighted lever 39 to turn counterclockwise (as viewed inFig. 1) under urge of the spring 41 and reducing the eii'ective forcearm of the weight 4I with respect to the cross shaft 99. Upon settingthe motor shaft Il in rotation the centrifugal force on the weight 4|will tend resilience of the hinge to turn the auxiliary lever I8counter-clockwise (as viewed in Fig. l) about the cross-shaft Il. andsince the lower end of the lever 3l bears 0n the adjusting screw 45there will be an inward pressure on the contact-carrying lever 9i,opposing the pressure of the hinge spring I4 and tending to separate thelever contacts 31 from the frame contacts 29. Upon the attainment of acertain critical shaft speed, determined by the spring 94 and force armof the weight 4I, the centrifugal turning moment produced by the weight4I will become sumcient to move the lever 3| inwardly and cause thelever contacts I1 to move out of engagement with the frame contacts 29.As a result, the electric circuit through the brushes 2l and 24 will beinterrupted by the separation of these contacts. If it is desired tohave the centrifugal switch operate at a lower speed-setting. the screw4I is turned inwardly, as to the position seen in Fig. 6, causing theweighted lever to swing clockwise (as viewed in Fig. 6) and inwardlyflexing the spring ,41. 'I'he contacts will then separate at a somewhatlower critical speed determined by the reduced effective force of thehinge spring I4 and the increased force arm of the weighted lever 99. Byturning the screw 44 inwardly from the position of Fig. 1 to theposition of Fig. 6. the speedsetting of the switch will be progressivelyreduced through a wide range. If the screw is moved inwardly a sumcientdistance, the lever contacts 3| will remain separated from the contacts29, even when the switch is at rest, and if Athe screw is movedoutwardly a sumcient distance, the contacts will remain in engagementregardless of the speed of the shaft. In the latter case the force armof the weight member 4I will be zero or very small.

In the arrangement shown in Fig. l, the centrifugal switch is employedto control the seriestype electric motor Il by which it is driven. Assoon as the motor` accelerates to the critical speed, the contacts 2land I1 separate, thereby introducing the resistor I3 in series with themotor windings. The motor speed then drops slightly below the criticalspeed. whereupon the contacts29andl1againengagetocaiuethe motor speed toincrease. In practice. the oscillatory contact-carrying lever 3| of theswitch vibrates at a relatively high frequency. and al a result theadjusted motor speed remains substantially constant.

It will be noted that the speed-setting of the lcentrifugal switch isaifected by two factors, one

the variation of the effective spring action on the oscillatorycontact-carrying lever 3l and the other the variation of the effectiveforce arm of the centrlfugalLv 'actuated weighted lever 8l. As a resultof these two factors. and especially the latter. the switch will operatein a satisfactory manner over a wide range of speed adjustments. At highspeeds tion is relatively strong and the eective force arm of theweighted lever Il is relatively short, thus avoiding excessivecentrifugal action. At low speeds the effective spring action isrelatively weak and the eiiective force arm of the weighted lever Il isrelatively long. thus obtaining the eifective spring ac- A sive windagelosses.

replaced if shown in Figs. 7 and 8, the pivot a favorable centrifugalaction on the weighted lever.

The plate-like contact-carrying members of the switch extend in planesapproximately normal to the shaft axis, thus providing for eiiicientcooling of the off-center contacts without exces- The construction ofthe switch readily permits the use of a plurality of contact pairs so asto provide adequate currentcarrying capacity, and the contacts can beeasily necessary. The switch is of such construction that it can beeconomically manufactured, the parts thereof being capable ofinexpensive fabrication and easy assembly.

In the modified form of centrifugal switch `shaft 39 and spring 41 ofFig. 2 are omitted, and the weighted lever |38 (corresponding to thelever 38) is hingedly carried on the forked oscillatory lever 3l bysprings 39. The springs are here shown to be leaf springs of E-shapedconfiguration, the free ends of the outer arms of the springs beingsecured by short riveted posts or studs it@ to the oscillatory lever,and the 'free ends of the intermediate arms of the springs being securedto. side extensions it of the weighted lever. The connecting bars of theE-shaped springs are in alignment and extend transversely of theoscillatory lever. The angular displacement of the weighted lever |38 bythe adjusting screw 45 is yieldingly resisted by the hinge springs i3d.The construction and operation of the switch of Figs. '7 and 8 areotherwise the same as that of Figs. l to 6.

The modified form of centrifugal switch shown in Fig., 9 is generallysimilar to that of Figs. l to 6 except that the contacts have beenreversed so as to be normally open, thus adapting the switch to be usedin various circuits requiring this contact relation. For lthis purposethe contacts 29 are reversed on the spring-mounted oscillatory lever 3lto face the insulating disk i9 and to engage cooperating contacts itldetachably mounted on a at annular supporting frame itl secured to thedisk i9 and outer collector ring 2| by spacing studs or posts V25 andassociated screws E26. The studs B25 correspond to the studs 25 ci Fig.3, and the frame lil corresponds to the plate 21 of Fig. 3. The contacts29 and H31 of the switch of Fig. 9 are normallyopen,

vand upon attainment of a critical shaft speed,

the centrifugally actuated weighted lever te causes the contacts toengage. The construction and operation are otherwise the same as that ofthe switch of Figs. 1 to 6. The modification shown in Fig. 9 may alsobe'applied to the switch of Figs. '7 and 8.

Certain embodiments of the invention have been shown and described, butit will be obvious to those skilled in the art that modifications may bemade without departing from the spirit and scope of the invention. f

What I claim as new and Letters Patent is:

l. In a centrifugal switch, the combination of a rotatable member, acontact carried by said member, a lever swingably mounted on said membervand movable in a generally axial direction with respect to said member,said lever being spring-urged in one direction, a contact carried bysaid lever and cooperating with said firstnamed contact, a weight memberhaving a pivdesire to secure by d otal mounting on said contact-carryinglever to swing about an axis transverse to the axisof said rotatablemember and centrifugally actuated to urge said contact-carrying lever ina direction opposite to its spring-urged direction, means for angularlydisplacing said weight meter with respect to said contact-carrying leverto adjust the effective arm of force of said weight member with respectto said lever,'and resilient means normally urging said weight member ina direction reducing said arm oi force.

2. In a centrifugal switch, the combination of a, rotatable member, aco'ntact carried by said member, a lever swingably mounted on saidmember and movable in a generally axial direction with respect to saidmember, said lever being spring-urged in one direction, a contactcarried by said lever and cooperating with said rstnamed contact, aweight member having a pivotal mounting on said contact-carrying leverto swing about an axis transverse to the axis of said rotatable memberand centrifugally actuated to urge said contact-carrying lever in adirection opposite to its spring-urgeddirection, angularly displacingsaid weight member with respect to said contact-carrying lever to adjustthe eiective arm of force of said weight member with respect to saidlever, and resilient means normally urging said weight member in adirection reducing said arm of force, said resilient means being carriedon said lever to reduce the biasing force on said lever when the arm offorce of said weight member is increased.

3. lin a centrifugal switch, the combination of a rotatable member, acontact carriedtby said member, a lever swingably mounted on said memberand movable in a generally axial direction with respect to said member,said lever being spring-urged in one direction,- a contact carried bysaid lever and cooperating with said first-named contact, a weightmember having a spring hinge connection with said lever to swing vaboutan axis transverse to the axis of said rotatable member andcentrifugally actuated to urge said lever in a direction opposite to itsspring-urged direction, and means for angularly displacing said weightmember with'respect to said lever to adjust its effective arm of forcewith respect to said lever, said spring hinge connection normally urgingsaid weight member in a direction reducing said arm oi force.

d. In a-centrifugal switch, the combination of a rotatable member, acontact carried by said member, a lever swingably mounted on said memberto move in a generally axial direction with respect to said member, saidlever being spring-urged in one direction, a contact carried by saidlever and cooperating with said firstnamed contact, a centrifugallyactuated weight member pivotally carried by said lever for urging saidlever in a direction opposite to its springurged direction, the pivotalaxes of said weight member and lever being generally parallel andextending transversely of the axis of rotation of said rotatable member,and means for angularly member to move in a generally axial directionwith respect to said member, said lever being spring-urged in onedirection and having forked free end portions forming an opening betweenthem, contacts carried by the forked portions of means forthe lever andcooperating with said rst-named contacts. a centriiugally actuatedweight member pivotally carried by the forked portions o! the lever andmovable in said opening, and means iorangularly shifting said weightmember with respectto said lever to adjust the arm ot i'orce oi' saidweight member and to thereby adjust the speed setting o! the switch.

6. In a centrifugal switch, the combination of a rotatable member, aframe mounted on said member and having an opening. contacts carried bysaid frameon opposite sides of said opening, a lever swingably mountedon said member to movein a generally axial direction with respect tosaid member, said lever being spring-urged in one direction, contactscarried by said lever and cooperating with said mst-named contacts. anda centritugally actuated weight member mounted on said lever for urgingsaid lever in a direction opposite to its spring-urged direction, saidweight member being movable in the opening oi' said frame.

7. In a centrifugal switch, the combination of a rotatable member, acontact carried by said member, `a lever swingably mounted on saidmember to move in a generally axial direction with respect to saidmember, a contact carried by said lever and cooperating with saidilrst-named contact, said lever being spring-urged in a direction toeilect disengagement of said contacts, a centriiugally actuated weightmember shiitably carried on said lever i'or urging said lever incontact-closing direction, and means ior shifting said weight memberwith respect to said lever to adjust the arm ot torce of said weightmember and to thereby adjust the speed setting oi' the switch.

8. In a centrifugal switch. the combination oi' a rotatable membercarrying a pair oi' contacts, resilient biasing means for one of saidcontacts, centriiugally actuated means carried by said member forrelatively displacing said contacts and including a shiftably mountedweight member having a variable arm oi' force. resilienty means normallyurging said weight member in a direction reducing said arm oi' force,and means to adjust said arm of force to thereby vary the speed settingof the switch.

, ROYAL LEE.

